Cartridged projectile typically refers to a projectile seated at a mouth of a cartridge case, which contains a propellant. Ignition of the propellant is typically by percussion or electric means. When the propellant burns, it generates high pressure gases within the cartridge case. The high pressure gases are then vented to a low pressure chamber located behind the projectile to eject the projectile from the cartridge case and then propel the projectile through a barrel of the weapon.
It is known that high pressure containment in the cartridge case is necessary for complete and reliable burning of the propellant. Attempts have been made to provide pressure containment in the cartridge case. For example, U.S. Pat. No. 7,004,074, assigned to Martin Electronics, describes a hemispherical burst cap 14 disposed at the mouth of a cartridge case 12; this is shown in FIG. 1. An inside surface of the hemispherical burst cap 14 has embossed lines. In use, after the propellant is ignited, pressure in the cartridge case 12 builds up to many atmospheres until the embossed lines on the burst cap 14 rupture. The high pressure gases are then vented in a metered manner through the ruptured burst cap to propel the projectile 10 through the gun barrel. However, it appears that pressure containment of this cartridge case has reached its limit and this cartridged projectile can only reach a conventional muzzle speed of up to about 75 m/s.
There is a need to provide an improved cartridged projectile that can reach a higher muzzle speed of about 100 m/s or more. A higher speed projectile will have a trajectory that is flatter than a low velocity projectile; this translates to improved accuracy with a higher speed projectile. However, the higher speed projectiles must retain the profiles of conventional projectiles so that they are usable on existing weapons. At the same time, recoil on the weapon must be acceptable for handheld weapons.